JPH05278247A - Melt-type thermal transfer recording method and device - Google Patents

Abstract

PURPOSE:To reduce an occurrence of a missing of ink (a void) even if recording paper has a rough surface. CONSTITUTION:In accordance with a smoothness of a recording paper surface, recording paper is classified to high-quality paper, plain paper, and rough paper. A pixel size at the time of thermal recording is increased with the increase of the roughness of recording paper in use. With the increase of the roughness of recording paper, the length of an ink dot in a main scanning direction is increased and, therefore, an ink dot adheres to the recording paper in a larger area. In this manner, an occurrence of a void is reduced even if recording paper has a rough surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fusion type thermal transfer recording method and apparatus suitable for recording halftone images.

[0002]

2. Description of the Related Art A melting type thermal transfer recording method uses a thermal head in which a large number of heating elements are arranged in the main scanning direction and presses it against the back of an ink film to transfer the softened or melted ink to a recording paper. Is. In this fusion type thermal transfer recording method, the amount of ink transferred onto the recording paper cannot be adjusted according to the amount of heat, and is therefore used for recording binary images such as line drawings and characters. The applicant of the present invention uses an elongated heating element in the main scanning direction, and controls the energization time of the heating element, the magnitude of the current, the number of drive pulses, etc. to control the direction of ink dots recorded in a pixel in the sub-scanning direction. A method of recording a halftone image by changing the length of the image has been proposed (for example, JP-A-3-219969).

[0003]

The recording paper used in the above-mentioned melting type thermal transfer recording method has a smooth recording surface in order to reliably transfer the ink. For this reason, when a recording paper having a rough recording surface is used, there is a problem that a portion (void) where the ink should not be transferred is originally generated, and a good image quality cannot be secured.

The present invention is intended to solve the above-mentioned problems, and fusion type thermal transfer recording capable of recording a halftone image in which the voids are not conspicuous even on a rough recording surface having a low smoothness. It is an object to provide a method and a device.

[0005]

In order to achieve the above object, according to the present invention, the coarser the smoothness of the recording surface of the recording paper, the lower the pixel density in at least the main scanning direction and the larger the area per pixel. And recorded it.

According to a second aspect of the present invention, in the fusion-type thermal transfer recording apparatus, the means for inputting the smoothness of the recording surface of the recording paper and the coarser the smoothness of the recording surface, the pixel density in at least the main scanning direction. So as to reduce the smoothness of the recording surface and a pixel density corresponding thereto, a means for obtaining the corresponding pixel density from the storage means based on the input smoothness, and a pixel density Accordingly, the heating elements corresponding to one pixel are driven as a unit to record image data.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 2 to 4 show recording states of gradation images. The thermal head 10 includes a heating element array 11 extending in the main scanning direction, and the heating element array 11 includes a plurality of heating elements 11a, 11b, 11c ,. Each heating element has an elongated shape with a length A in the main scanning direction and a length B in the sub scanning direction. For example, A is 84
μm and B is 40 μm.

The thermal head 10 and the recording paper 14 are
The relative movement is made continuously or intermittently in the sub-scanning direction. An ink film 15 (see FIG. 6) is in close contact with the recording paper 14, and the melted or softened ink is transferred to the recording paper 14 by heating the thermal head 10 from behind the ink film 15. The melted ink forms ink dots 17 indicated by hatching in each pixel 16. In this embodiment, the feed pitch of the thermal head 10 is 4 μm, and each ink dot 17 increases from 40 μm by 4 μm.

The pixel density in the main scanning direction changes according to the smoothness of the recording surface of the recording paper 14, as shown in FIG. That is, as shown in FIG. 2, high-quality paper 14 with high smoothness is provided.
When using, the pixel density in the main scanning direction is 12 dots / m in order to record one pixel 16 with one heating element.
m. The pixel size at this time is A × L1 in length in the main scanning direction and the sub scanning direction. Here, the length L1 in the sub-scanning direction is electrically controlled,
If the pixels are square, the size is, for example, 84 × 84 μm.
As shown in FIG. 3, when the plain paper 14a is used, the pixel density in the main scanning direction is 6 dots / mm because two adjacent heating elements form one pixel 20. The pixel size at this time is 2A × L2 (for example, 168 × 168 μ) in the main scanning direction and the sub-scanning direction.
m). Further, as shown in FIG. 4, when the rough paper 14b is used, one pixel 21 is formed by three adjacent heating elements.
Therefore, the pixel density is 4 dots / mm.
The pixel size at this time is 3A × L3 (252 × 252 μm) in the main scanning direction and the sub scanning direction.

As described above, the recording papers 14, 14a used,
The length of the ink dots 17, 17a, 17b in the main scanning direction is changed according to the smoothness of the recording surface of 14b. Since it is longer than the high smooth surface, as shown in FIG. 5, even if the surface is rough, the ink adherence is improved by the length of the ink dot, which results in the void 2
3 is less likely to occur. That is, short ink dot 1
In No. 7, the number of adhering points is reduced due to the unevenness of the surfaces of the plain paper 14a and the rough paper 14b, and the voids 23 are thereby generated. In addition, the ink dots 17 formed by the two heating elements
In the case of "a", the plain paper 14a is good without the generation of the voids 23, but when the rough paper 14b is used, the number of attached portions is reduced due to the unevenness, and the voids 23 are generated. Also,
In the case of the ink dot 17b composed of three heating elements,
Even with the rough paper 14b, the voids 23 do not occur because the number of adhering points increases as the length of the rough paper 14b increases.

FIG. 6 shows a fusion type thermal transfer printer embodying the present invention. The recording paper 14 is wound around the outer periphery of the platen drum 25, and the leading end is fixed by a clamp member 26. This platen drum 2
5 is a constant pitch (4 μ
m) is rotated intermittently. When the ink surface of the ink film 15 is in close contact with the recording paper 14, the guide roller 2
Moved along 8,29. These guide rollers 2
The thermal head 10 is arranged between 8 and 29 to heat the ink film 15 from behind.

Image input unit 3 such as a TV camera or a scanner
The image data of the gradation image taken in from No. 1 is converted from an analog signal to a digital signal by the A / D converter 32 and is once written in the frame memory 34. The image signal of each pixel read from the frame memory 34 is sent to the image signal processing unit 35, where the gradation is corrected. A mode selector 37 is connected to the controller 36. The mode selector 37 is provided with a recording paper selection knob 38. By operating the recording paper selection knob 38, three types of high-quality paper with high smoothness, plain paper with medium smoothness, and rough paper with low smoothness are provided. Is sent to the controller 36.

The controller 36 controls the thinning circuit 40 by this recording paper mode signal and sends the image signal as it is to the table memory 41 without thinning the data in the high quality paper mode. In the plain paper mode, even-numbered data is thinned out in the X and Y directions, the thinned out even-numbered data is replaced with adjacent odd-numbered image data, and this image signal is written in the table memory 41.
Furthermore, in the rough paper mode, the data is thinned out at a ratio of two to three in the X and Y directions, and the data of the thinned portion remains 1
This image signal is written into the table memory 41 by replacing it with individual image data.

The table memory 41 stores gradation control data in advance, converts the image data of each pixel into drive time data for driving each heating element of the thermal head 10, and stores it in the line buffer memory 42. To do. The image data for one line from the line buffer memory 42 is sent to the gate 43 for each line. A pulse generator 45 is connected to the gate 43. Pulse generator 4
As is well known, the reference numeral 5 generates a steady pulse composed of one rising pulse having a long cycle for raising the heating element to the ink melting temperature and a pulse train having a short cycle for keeping the temperature of the heating element at a constant level. .. Then, the gate 43 outputs a drive pulse to the driver 46 by passing a stationary pulse in which the length of the pulse train is changed according to the length of the drive time data from the line buffer memory 42. The driver 46 drives the thermal head 1 according to the drive pulse.
0 is driven to heat each heating element for a predetermined time. As a result, a halftone image is recorded on the recording paper 14.

The controller 43 further rotates the platen drum 25 via the driver 47 and the pulse motor 27 in synchronization with the driving of the thermal head 10. As a result, in the case of high-quality paper having a flat recording surface according to the smoothness of the recording surface of the recording paper 14, as shown in FIG. 2, a square (84 of length A of the heating element having one pixel size) is used. × 84μ
m), and a halftone image having a pixel density of 12 dots / mm is recorded. In the case of plain paper, as shown in FIG. 3, a pixel size is a square (168 × 168 μm) having a heating element length of 2 A and a halftone image with a pixel density of 6 dots / mm is recorded. It In the case of rough paper, as shown in FIG. 4, a halftone image having a pixel size of 3 and a pixel density of 4 dots / mm is recorded.

Although the above embodiment is a line printer, the present invention can also be applied to a serial printer. In this serial printer, the thermal head moves in the sub scanning direction and the recording paper moves in the main scanning direction. The present invention can also be applied to a color printer that uses cyan, magenta, and yellow ink films.

[0017]

As described in detail above, according to the present invention, the coarser the degree of smoothness of the recording surface of the recording paper, the lower the pixel density in at least the main scanning direction and the larger the area per pixel. Since the recording is performed, the ink is reliably transferred by increasing the adhesion area even on the recording paper having a rough recording surface, so that the occurrence of voids (ink loss) can be reduced.

[Brief description of drawings]

FIG. 1 is a flow chart showing a fusion type thermal transfer recording method of the present invention.

FIG. 2 is an explanatory diagram showing a thermal head and ink dots recorded by the thermal head on high-quality paper.

FIG. 3 is an explanatory diagram showing a thermal head and ink dots printed on plain paper by the thermal head.

FIG. 4 is an explanatory diagram showing a thermal head and ink dots recorded on the rough paper with the thermal head.

FIG. 5 is an explanatory diagram schematically showing the transfer state of each ink dot according to the roughness of the surface of the recording paper.

FIG. 6 is a block diagram showing an outline of a fusion type thermal transfer recording apparatus of the present invention.

[Explanation of symbols]

 10 Thermal Head 11 Heating Element Array 14, 14a, 14b Recording Paper 16, 20, 21 Pixels 17, 17a, 17b Ink Dots

Claims (2)

[Claims] 1. A fusion type thermal transfer recording method for recording an image on a recording sheet using a thermal head in which a plurality of heating elements are arranged in the main scanning direction, wherein the coarser the smoothness of the recording surface of the recording sheet is, the main scanning is performed. 1. A fusion-type thermal transfer recording method, wherein recording is performed by reducing the pixel density in the direction and increasing the area per pixel. 2. A fusion type thermal transfer recording apparatus for recording an image on a recording sheet by using a thermal head having a plurality of heating elements arranged in the main scanning direction, and means for inputting a smoothness of a recording surface of the recording sheet, Based on the input smoothness, means for pre-storing the relationship between the smoothness of the recording surface and the pixel density corresponding thereto so that the coarser the smoothness of the recording surface is, the lower the pixel density in the main scanning direction is. A means for obtaining the corresponding pixel density from the storage means and one heating element for one pixel according to this pixel density
A fusion-type thermal transfer recording apparatus comprising: a unit that is driven as a unit to record image data.